Many engines, particularly those in commercial service, spend a substantial amount of time idling; i.e., running while the vehicle is stationary. Many factors contribute to extended periods of engine idling. Under some circumstances, the driver does not desire to shutdown the engine, even if it will be running at idle for comparatively long periods. One example is a delivery truck making frequent, but relatively short stops. It is not unusual for the driver to leave the engine running during these short stops even though fuel could be saved by stopping and restarting the engine. Typically, the driver does not want to be inconvenienced or otherwise delayed. Still others believe that stopping and restarting an engine can use more fuel than what they perceive the engine will consume during the delivery stop. Another reason that a driver might keep the engine running at idle speed is to keep other vehicle systems energized; such systems can include air brakes, air conditioning systems, audio systems, PTO, and the like. Still further, extended engine idling may be experienced in heavily congested areas where traffic is frequently at a standstill.
Under many of these conditions, it is desirable to have a mechanism (method or device) by which the engine can be automatically, safely shut down after idling (i.e., running without vehicle motion) for a certain period of time, to prevent wasteful and unnecessary consumption of fuel.
Certain factors make an engine idle shutdown routine desirable in an automatic shutdown system. One of these factors is the engine temperature. If the engine is shutdown above certain temperatures, for example above 200° F., there is potential for engine damage. A cool down period would be advantageous to allow the engine to reach a safer shutdown temperature. Properly shutting down the engine can extend the life of the engine and other connected components, which is highly desirable. Another factor relates to laws or regulations prohibiting extended engine idling, such as in cities or other populated areas, or in locations where the vehicle is positioned near ventilation air intake systems. An example of the latter is a loading dock where a driver might be tempted to leave his truck idling, but near air-conditioning intakes, which might undesirably take up exhaust from idling delivery vehicles.
On a more general note, exhaust from idling vehicles is a pollutant and is undesirable. Reducing pollution, complying with laws and regulations, and conserving fuel are attributes which reflect well on the operator, vehicle manufacturer, and vehicle owner (whose name is often emblazoned on the vehicle). Also, in vehicles having hybrid drives (an internal combustion engine coupled with an electric machine, for example), it is desirable to shutdown the internal combustion engine quickly for fuel economy. Therefore, an automated engine idle shutdown mechanism is desirable as it turns the engine off after certain preconditions are met.
Stopping the engine quickly is also desirable for vehicles with exhaust aftertreatment devices with catalysts, e.g., catalyzed diesel particulate filters or selective catalytic reduction devices. These devices require high catalyst temperatures to be operational, the so-called “light off” temperature. Extended idling can cool the catalyst by flowing relatively cool idle exhaust over the catalyst, requiring a heating period after restarting the engine. The catalyst cools relatively slowly with the engine off, so quickly shutting down the engine can allow the aftertreatment catalyst to more quickly reach light off temperature after a restart.
U.S. Pat. No. 4,088,110 to Sperline discloses a system having a timer control that delays shutdown after receiving a manual signal (e.g., key turn) for a set time duration to allow the engine to cool. The patent does not disclose sensing or monitoring temperature, and may continue idle for too short a time, which may subject the engine to damage, or too long a time, which is wasteful.
U.S. Pat. No. 4,656,973 to Endres discloses a system that is activated when the operator turns the ignition key to shut down the engine. The system senses engine temperature and will override the key shutdown if the engine temperature is above a pre-set shutdown temperature, and continue to run the engine until the engine temperature is below the pre-set temperature.
U.S. Pat. No. 6,227,153 to Till expressly incorporated herein by reference, discloses an apparatus and method for cooling an engine after shutdown but prior to engine maintenance work for work personnel safety. The '153 patent discloses providing an operator with a key to activate a cool down mode in which the coolant pump and fan are active. Using ambient and engine coolant temperatures, the system determines when the engine has cooled to a temperature sufficiently low to minimize injury to maintenance personnel. However, there is a large variation in the amount of time it takes for the engine to actually shut down. This is caused by the inclusion of a “maximum engine coolant temperature” parameter, which prevents the engine from actually shutting down until the coolant temperature has reached a certain temperature considered to be safe for engine shutdown. Depending on engine and ambient temperatures, there can be as much as a 30 minute variation in overall time elapsed before actual shutdown.
There is a need for improvement in engine idle shutdown apparatus and thermal management methods which integrate with the vehicle's existing systems, monitor various vehicle parameters, and safely and rapidly shut down the engine when prescribed idle conditions exist. These idle shutdown mechanisms need to accomplish the prescribed shutdowns without risk of damage to the engine or associated components, and within a consistent time frame, even when being affected under widely varying vehicle and ambient conditions.
The need for improvement may be illustrated by way of the example of a typical conventional vehicle idle shutdown routine. The idle shutdown procedure begins at t=0, at which point a shutdown timer is activated to time a controlled idle period. After the timer expires, the engine is shutdown. In this example, the vehicle engine coolant temperature is 209° degrees Fahrenheit when the initial idle shutdown conditions are met and the shutdown system is turned on. The vehicle engine cooling fan is off. Because the initial temperature is above 200° degrees Fahrenheit, however, idle shutdown timing is suspended (made inactive) until the engine coolant temperature decreases below a threshold temperature (to prevent engine damage). In this example, the ambient air temperature is above 80° degrees Fahrenheit, which results in slow heat transfer from the engine to the environment, with the temperature decreasing only two degrees Fahrenheit over the first 330 seconds. At this time the engine cooling fan activates, resulting in the vehicle engine coolant temperature decreasing six degrees Fahrenheit in the next 80 seconds. At t=550 seconds, the idle shutdown timer 1 switches from inactive to active status, turning off the engine automatically after a period of 300 seconds has elapsed. Engine load has not changed during this process, remaining at approximately ten percent.
This situation is undesirable since the operator activated the idle shutdown device at t=0, but because the engine coolant temperature was above 200° degrees at t=0, the idle shutdown timer was on hold, or inactive, until the engine coolant temperature decreased to 200° degrees Fahrenheit, at t=550. The idle shutdown timer then switched to active, and shuts the engine down 300 seconds (five minutes) later. Thus, the operator believed that the engine would shutdown 540 seconds (nine minutes) sooner than it did, which could result in violation of laws or regulations, wastes fuel, and adds wear and tear to the engine and its components. As a result, the operator loses faith in the typical idle shutdown device.
In at least one embodiment, the presently disclosed solution takes the form of a method for controlling an automatic shutdown process that promotes cooling down an internal combustion engine of a vehicle to a predetermined safe shutdown temperature when vehicle-idle conditions are detected. The method includes initially determining that vehicle-idle conditions exist. At a minimum, these conditions include making a determination that the engine of the vehicle is running at idle speed. An engine-associated temperature is then measured and it is determined whether the measured temperature is above a first temperature value, said first value being defined according to the risk of engine damage if shutdown at that temperature, as explained in greater detail hereinbelow. In this regard, the engine-associated temperature may relate to any number of engine systems or components, however, for the purposes of clarity of description, the present disclosure primarily focuses on engine coolant temperatures.
Responsive to determining that the measured temperature is above the first threshold, a cooling fan associated with the engine is operated. The engine-associated temperature is monitored and cooling fan operation is reduced when the engine-associated temperature is determined to have decreased below the first threshold temperature value. Typically, the reduction in fan operation will be to zero speed, or stopped, but it is contemplated that the fan may be merely slowed below the operational speed previously affected. Ultimately, engine shutdown is completed when predetermined shutdown conditions are determined to exist, and which may include the vehicle not moving (i.e., stationary), the transmission in neutral or out of gear, the engine at idle speed, and the engine-associated temperature being below the first threshold temperature value.
The invention further contemplates additional cooling action if the engine-associated temperature is above a second threshold value higher than the first threshold temperature. Responsive to this condition, the fan is operated and engine speed is increased above idle speed to increase fan speed to more rapidly cool the engine. When the engine-associated temperature decreases to below the second threshold temperature, engine speed is returned to the idle speed, and the fan continues to operate while the temperature is above the first threshold temperature. A programmed control system is utilized to control the occurrence, level, and time period during which increased engine speed is affected while the cooling fan is engaged, the control managing these parameters so to decrease the engine-associated temperature.
The invention contemplates that a time delay period can be initiated after the engine-associated temperature is determined to have decreased below the first threshold temperature value before engine shutdown is completed. A delay allows an opportunity to notify an operator of the impending shutdown and permit an override signal to be made and acted on. For example, during this time delay the driver of the vehicle may override engine shutdown if, for example, the vehicle is operating in heavy stop-and-go traffic and shutdown is not desirable.
According to the present disclosure, the determination of whether vehicle-idle conditions exist also considers whether the vehicle is stationary. If the vehicle is stationary, then the engine shutdown sequence is initiated.
A preferred embodiment relies on the method utilizing an onboard microprocessor-based control system to automate the engine cool down and shutdown procedures. Those persons skilled in the art will recognize that one or a combination of resident or added computerized controllers may be utilized to implement the prescribed shutdown procedures described herein. In at least one alternative, parameters of the engine cool down and shutdown procedures are programmable and therefore customizable by the vehicle operator, which is not necessarily limited to the driver of the vehicle, but also includes owners, fleet managers, and others having authority.
As an alternative, the engine-associated temperature may be taken as a direct temperature measurement obtained from a sensor located directly on the engine. Still further, the engine-associated temperature may be measured from circulated engine oil, other engine components, engine fluids, engine air intake or exhaust gases, or elsewhere in the engine compartment.
According to the presently described example of the shutdown cooling process, the cooling fan which is associated with a heat dissipating radiator of the vehicle is controlled between on and off operating states in which a substantially constant fan speed is maintained in the on operating state and the cooling fan is essentially stopped in the off operating state. As an alternative, however, the cooling fan may be run at variable speeds depending on the determined engine-associated temperature and/or the ambient temperature. An electric motor driven, fluid motor driven fan, or other variable speed drive may be used for such capability.
As yet another alternative, a variable speed coolant pump may be provided and operated at a selected speed depending on the determined engine-associated temperature and/or ambient temperature to more quickly reduce the engine-associate temperature to an appropriate shutdown temperature.
The first and second threshold temperatures define three temperature zones. A first zone, which is below the first threshold temperature, defines a temperature zone within which the engine may be shutdown without risk of damage from engine heat. In some systems, the first threshold temperature coincides approximately with a thermostat-open temperature of a cooling system of the vehicle, which is generally a safe temperature for safe engine shutdown. A second zone, which is above the first threshold temperature and below the second threshold temperature, defines a temperature zone where shutdown risks engine damage, and within which the cooling fan driven by the engine at idle is effective to cool in the engine in a reasonable time. The third zone is above the second threshold temperature and defines an engine temperature range where shutdown would result in serious damage to the engine and maximum cooling is needed.
Utilizing the cool-down procedures outlined herein, a total rapid engine cooling time period of as little as five minutes can be safely effected, the time being measured from when vehicle-idle conditions are first determined to exist, and the shutdown is initiated, and continuing during engine cooling control until engine shutdown is completed. In this manner, regulations that prescribe such time limits can be attained. Heretofore, such regulatory time limits have been on the order of ten to thirty minute shutdown periods, which the presently disclosed method and procedure handily accommodate, but more stringent restrictions are predicted on the order of five minutes which can be similarly accommodated, and which have been previously out of reach without causing heat damage to the engine in some circumstances.